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New form of mastitis found in Louisiana

HOMER, La. — A form of mastitis previously unreported in Louisiana has been detected and could prove costly to the state’s $72 million dairy industry if not contained.

Bill Owens, an LSU AgCenter microbiologist in the AgCenter’s mastitis lab at the Hill Farm Research Station, Homer, La., said the disease is called “mycoplasma mastitis.” While it poses no threat to humans, it is highly contagious in dairy cows and could be economically devastating to dairy farmers.

The LSU AgCenter, in conjunction with the Louisiana Department of Agriculture and Forestry, has been testing every dairy herd in the state since March. The tests will continue until March 2005.

“Milk is the most regulated food we have,” Owens said. “Because of this, it is also the safest food. One benefit of this test is that the farmer gets a monthly report that shows the status of mastitis in his herd. The results also are available online.”

Louisiana dairy farmers pay $15 for the test, which tests for mycoplasma mastitis, as well as other forms of mastitis. Each bulk tank sample is tested for all mastitis pathogens, and the information is made available to dairy farmers through the LSU AgCenter’s agents.

As a result, even dairies with no mycoplasma mastitis benefit from the program by receiving monthly mastitis reports on their herds, which they can use to control all forms of mastitis and improve their profitability, Owens said.

Milk from cows with severe mastitis is not allowed in milk that is sold to the public, said Gary Hay, an LSU AgCenter dairy expert. About 829 million pounds of milk were sold by Louisiana milk processing plants in 2003.

“This mycoplasma monitoring program is strictly an animal health issue,” he said. “The state Livestock Sanitary Board wants to make sure herds that may have cattle infected with mycoplasma don’t spread the disease to other herds, because this disease can be devastating to the economic health of a dairy.”

Dr. Maxwell Lea, state veterinarian with the Louisiana Department of Agriculture and Forestry, said so far mycoplasma mastitis has been found in only four of Louisiana’s 312 dairy herds since testing began in March.

“I don’t have a number of cows that have been culled (removed),” Lea said. “The decision to cull is left up to the individual dairy owners.”

The spread of mycoplasma mastitis can be greatly reduced if good milking procedures are followed, Owens said. Using teat dips is one method. “Each cow’s teats should be dipped before and after milking,” he said. “Farmers should also disinfect the milking units between cows.”

Another way to prevent the spread of mycoplasma mastitis is to test prospective cows before buying them and putting them into a herd, he said. It takes about a week to receive the results from a mycoplasma mastitis test.

“There are about 100 different types of mastitis,” Owens said. “This particular type has been found in other areas of the United States and just recently became a problem in Louisiana.”

There is no treatment for mycoplasma mastitis, which is spread primarily from cow to cow during the milking process. “It can also be passed from the mother cow to her female calf,” Owens said. “And, it can be spread by nasal secretions.”

Detection and control of mycoplasma require testing of all milk herds in Louisiana. “Bulk samples are taken from each herd and tested each month,” Owens said. “We test the milk samples here, at the mastitis lab, and if we find any mycoplasma, we send it to the mastitis lab at the University of California at Davis for confirmation.”

If mycoplasma mastitis is detected, a new sample is gathered, and the herd is checked again, Owens said. Two samples must test positive before it is determined there is a problem, he said.

“If we get two positive tests from a bulk sample, we will check each cow in the herd,” he said. “The infected cow or cows, once identified, generally are sold for meat. Usually, not every cow in a herd is infected, and, if the infected cow(s) is taken out, the herd can be saved.”

Herds that have had cows infected with mycoplasma mastitis must get clear test results for six months before their cows can be sold as milk cows.

A. Denise Coolman writes for the LSU AgCenter (318–366–1477 or

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